81605713 has 4 divisors (see below), whose sum is σ = 93263680. Its totient is φ = 69947748.

The previous prime is 81605707. The next prime is 81605717. The reversal of 81605713 is 31750618.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 31750618 = 2 ⋅15875309.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81605713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81605717) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5828973 + ... + 5828986.

It is an arithmetic number, because the mean of its divisors is an integer number (23315920).

Almost surely, 2^81605713 is an apocalyptic number.

It is an amenable number.

81605713 is a deficient number, since it is larger than the sum of its proper divisors (11657967).

81605713 is a wasteful number, since it uses less digits than its factorization.

81605713 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11657966.

The product of its (nonzero) digits is 5040, while the sum is 31.

The square root of 81605713 is about 9033.5880468394. The cubic root of 81605713 is about 433.7506991991.

The spelling of 81605713 in words is "eighty-one million, six hundred five thousand, seven hundred thirteen".